The popularization of systems are expected which use electronic tags instead of barcodes and receive radio waves radiated from electronic tags to read product information. For example, by being equipped with a plurality of antennas for a tag reader and switching antennas to scan, it is possible to read information of plural tags at high speed (Patent Literature 1).
By the way, a set product in which a plurality of individual products are packaged, for example, a carton in which ten packs of cigarettes are contained is a unit for sale, and an electronic tag is stuck on the carton. However, when separately selling the individual products within a set product, i.e., a unit, electronic tags must be stuck on respective packs at a retail store, which is complicated. Therefore, it is desirable to stick electronic tags on both the carton and every inner at the factory.
Although the inside packs can not be seen from the outside, a tag reader can not distinguish on which of the outside and inside boxes electronic tags are attached. Thus, both of the electronic tag information is read through radio waves, and the problem of double counting occurs.
Specifically, when reading electronic tags of both of a carton of products and individual products for separate sale, there arise a problem in sale management because the tag reader cannot distinguish between a tag stuck on a product inside the carton and a tag stuck on a individual product for separate sale.
The problem of double counting will be solved by writing information regarding whether or not a product is for separate sale on each electronic tag and information that no counting of individual products in a carton which cannot be separated for sale.
However, in a case where set products are entered into a retail store to decide whether they are to be separately sold or not, it is necessary, at the stage of separate sales, to write information whether or not a separate sale is permitted for each electronic tag, which is complicated. Furthermore, there arises a problem of double counting when the writing is not performed because of forgetting the writing, the writing time being not enough, or a radio wave for writing being too weak.
Hereinafter, “set product” and “individual product” may include packages (wrapping paper, packaging bag or packaging container), and “the individual product” may not be packaged.
PATENT LITERATURE 1: Publication number 2000-187715 of Japanese patent application